JERUSALEM — As he was leaving the Perm Labor Camp in the Soviet Union's Ural Mountains on the first leg of his journey to freedom, dissident Anatoly Shcharansky lay down in the snow and said he would refuse to go unless his guards allowed him to take a pocket-sized Hebrew book of psalms that had helped to sustain him in prison.

His jailers, Shcharansky said in an Israel television interview here Wednesday night, "checked the book again, and then they gave it back to me. And that was the only thing I managed to take out of the Soviet Union."

The interview and a much briefer one on Israel radio were the Jewish activist's first since being released in a major East-West prisoner exchange Tuesday. They also marked his only public comments on his first full day on Israeli soil, a day that was otherwise spent in rest, a physical checkup and meetings with a handful of close friends.

Shcharansky had arrived aboard a special government plane to a hero's welcome in Israel on Tuesday night. It was about eight hours after he had walked across the Glienicke Bridge into West Berlin, and almost nine years from the day he was imprisoned in the Soviet Union because of his activities on behalf of human rights and Jewish emigration.

The dissident pledged in his first interviews that whatever else he decides about his future, "my obligation is first of all to use my experience in order to help the people who are left in the Soviet Union." His comments suggested that he will not feel constrained to silence because his 77-year-old mother and elder brother are still in Moscow.

Family May Follow

He told his television interviewer that he expects his mother to join him in Israel soon. "I understand that this was even part of the deal," he said. "And I hope that it is so. I hope that within a month she will be here." He said he last saw his mother more than a year ago.

In Washington, the State Department, in response to questions on the emigration prospects for the rest of the Shcharansky family, said without elaborating that "the Soviets have indicated they will allow his mother and other family members to emigrate."

Earlier Wednesday, Shcharansky spoke for an hour by telephone with his brother, Leonid, and he took the first steps towards making a formal request that the family be allowed to reunite in Israel.

Sitting beside Shcharansky during his interviews, and helping him when his limited Hebrew failed him, was his wife, Avital, who has traveled all over the world during the last 12 years, campaigning for her husband's freedom.

Quickly Partly

Avital Shcharansky left the Soviet Union one day after their marriage in July, 1974, believing that her husband would soon be allowed to join her. She was not to see him again until they were reunited Tuesday.

"We are all trying to respect their privacy," said Uri Savir, media adviser to Prime Minister Shimon Peres, in a briefing for foreign newsmen Wednesday.

Peres had greeted Shcharansky at the airport Tuesday night, lauding him as an "unbreakable" man who has shown that "you can arrest a body, but you cannot put in prison a spirit." Savir said that Peres and Shcharansky are expected to have a more extended private meeting "very soon."

Friends described the Shcharansky couple as "exhausted" Wednesday after the excitement of the dissident's release and the trip to Israel. They said that a doctor who examined Shcharansky in the morning had prescribed "lots of rest."

Savir said that while preliminary medical reports indicate that his condition is "satisfactory" under the circumstances, Shcharansky is expected to check into Hadassah Hospital within a few days for more extensive tests.

Gained 20 Pounds

Savir quoted Shcharansky as having told government officials Tuesday night that he had been given more and better food during the last several weeks of his imprisonment and that he had gained more than 20 pounds in that period.

In his television interview, Shcharansky told his interviewer that he had "very hard times" in prison--"problems with my heart and eyes as a result of long periods of solitary confinement."

He said he spent a total of more than 400 days in solitary confinement during his nearly nine years in Soviet prisons and labor camps. He spent his time trying to remember the Hebrew that he had learned before his arrest, he said. "I tried to remember every word and proverb."

Once, he said, he spent 130 straight days in a punishment cell despite a Soviet law that limits time in solitary to 15 days at a stretch.

The dissident said that on that occasion, his offense was going on a hunger strike to protest the confiscation of the tiny psalmbook, which his wife had sent in one of the few letters from her that actually were delivered to him.

'Helped Me to Endure'

"When they released me they took everything I had," Shcharansky told his interviewer. "And I said I would not leave the Soviet Union without my book of psalms, which helped me to endure what I endured."